In order to analyse samples, for example bodily fluids such as blood or urine, it is common to use analysis systems in which the samples to be analyzed are located on a test element, and optionally interact in a test field with one or more reagents on the test element before they are analyzed. The optical, in particular photometric, evaluation of test elements is one of the most commonly used methods for rapidly determining the concentration of analytes in samples. Photometric evaluations are widely used in the field of analysis, environmental analysis and above all in the field of medical diagnosis. Especially in the field of blood glucose diagnosis from capillary blood, test elements which are photometrically evaluated are of great value.
There are various forms of test elements. Essentially square sheets, also referred to as slides, in the middle of which there is a multilayer test field are known, for example. Diagnostic test elements which are of strip-shaped design are referred to as test strips. Test elements are described in the prior art, for example in the documents DE-A 197 53 847, EP-A 0 821 233, EP-A 0 821 234 or WO 97/02487. The present invention relates to test elements of any shape, and in particular strip-shaped elements.
Test elements in which a sample is applied to a sample application site, and is transported by means of capillary action to a detection zone (test field) separate from the sample application site, are known in the prior art. For example, DE 197 53 847 A1, published in English as CA2311496, which is hereby incorporated by reference in its entirety relates to such a test element. It describes an analytical test element for the determination of an analyte in a liquid. It contains an inert support, a detection element and a channel suitable for capillary liquid transport, which has a sample application opening at one end and a ventilation opening at the other end of the channel suitable for capillary liquid transport. The channel suitable for capillary liquid transport is formed at least partially by the support and the detection element, and extends in the capillary transport direction from the sample application opening at least as far as the detection element edge closest to the ventilation opening, a recess in a face which forms the channel suitable for capillary liquid transport being located on the test element edge forming the sample application element. The test element edge forming the sample application opening is thus interrupted at least partially on one side, and the face opposite the recess is free. The recess in a face forming the capillary channel on the edge of the test element is used to ensure that the sample liquid can enter the capillary channel. This is achieved in that the sample drop on the test element edge closest to the sample application opening, which is interrupted by the recess, can be brought directly in contact with one of the faces which form the inner surface of the capillary in their extension. By suitable choice of the geometry and dimensions of the recess, the liquid drop is very likely to come in contact with the active capillary zone and be readily sucked into the interior of the capillary, regardless of the exact position of the dosing.
For the analytical study of a sample on a test element, test element analysis systems are known in the prior art which contain a test element to position the test element in a measuring position, and a measurement and evaluation device for carrying out a measurement and determining an analysis result based on this. WO 00/19185 A1, which is hereby incorporated by reference in its entirety, relates to a device for the photometric evaluation of test elements, containing                an illumination unit having at least a first light source and a second light source,        a frame for receiving a test element with a detection zone, so that the detection zone is positioned opposite the illumination unit,        a detection unit having at least one detector, which detects light reflected by the detection zone or transmitted through the detection zone,        a control unit, which activates the two light sources and records the signal generated by the detection unit as a detection signal, and        an evaluation unit, which evaluates the detection signals in order to determine the analyte concentration contained in the sample.        
Known types of measuring apparatus have an opening, generally a slot, into which the test elements can be inserted. Guide elements ensure that a test element is inserted with the intended orientation. If the test element is introduced manually into the apparatus, design features of the apparatus must be provided which guarantee the desired positioning of the test element. This is usually done by a restriction which prevents insertion beyond a predetermined target position. Analysis systems which contain a storage container (magazine) with a multiplicity of test elements are furthermore known in the prior art. In this case, for example, a test element is transported from the storage container to the measuring position by a slide or plunger, and is automatically discarded from the analysis system after the measurement has been carried out.
DE 199 02 601 A1, published in English as U.S. Pat. No. 6,475,436 (B1), discloses a device for extracting a consumable analytical medium, in particular a test element, from a storage container which has one or more chambers containing consumable media. The chambers respectively have an extraction opening for extracting a consumable medium and an insertion opening, opposite the extraction opening, for introducing a plunger to transport the consumable medium. The extraction opening and the insertion opening are closed by a film in order to store the consumable medium. The device comprises a plunger which can be moved by means of a drive unit in order to extract a consumable medium.
Discarding the consumable test elements entails a contamination or infection risk since they are released without control into the environment and carry the rest of the sample material (for example blood, urine or interstitial fluid) on their surface. Hygienic handling and disposal of the test elements could be ensured by transport back into a storage magazine contained in the analysis system being used (re-magazining) or transport into a waste magazine intended for disposal of the test elements.
In the test element analysis systems known in the prior art, the test element in the measuring position rests via at least a large fraction of its lower side on a measuring apparatus surface in the analysis system. The lower side is pushed over the measuring apparatus surface during transport of the test element into and out of the measuring position. The test element is in this case guided by means of lateral guide faces which are perpendicular to the measuring apparatus surface. In a system for photometrically evaluating the test element, the measuring apparatus surface usually contains an optical window, below which the optics are located. Resting the test element via a large fraction of its lower side on the measuring apparatus surface has the disadvantage that a liquid sample applied to the test element, in the vicinity of one of its side edges, can stain the measuring apparatus surface. For example, a part of the liquid sample could be drawn by capillary forces between the test element and the measuring apparatus surface, so that a further region including the optical window is wetted with the sample. Such staining occurs in particular when the test element is being drawn back over the measuring apparatus surface into the magazine after the measurement has been carried out (re-magazining). In this case, any sample adhering to the test element edge used for the sample application will be wiped over the measuring apparatus surface.
The optical window of the analysis systems known in the prior art has to be sunk into the measuring apparatus surface in order to protect it against damage due to friction by the test element.